This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Glycogen Storage Disease GSD is a disorder of glycogen metabolism which results in hypoglycemia, lactic acidemia, hyperuricemia and hyperlipidemia Levy et al. 1987. While GSD patients manifest a pro-atherogenic lipid profile characterized by hypercholesterolemia, hypertriglyceridemia, and reduced HDL, the severe hyperlipidemia has not yet been correlated with an increased risk of early cardiovascular disease CVD. Consequently, the current standard of care does not recommend treatment with lipid lowering agents Ubels et al. 2002. Several theories have been postulated to explain the protective features in GSD patients such as increased cholesterol efflux, increased antioxidant potential, and decreased platelet aggregation Nguyen et al. 2005, Wittenstein et al. 2002, Muhlhausen et al. 2005. Despite the presence of dyslipidemia, there has been no comprehensive study to adequately assess cardiovascular risk in GSD patients. We hypothesize that hyperlipidemia places GSD patients at increased risk for early cardiovascular disease. Noninvasive measures of CVD using carotid intima media thickness IMT, brachial artery reactivity BAR, and radial artery tonometry RAT Fathi et al. 2001 will be performed on 100 patients with GSD and hyperlipidemia. BAR will be the primary outcome measurement of CVD. We will evaluate the proposed protective mechanisms with by measuring Apo proteins, free fatty acids, single plasma antioxidants and coagulation parameters. The data from this study may be generalized to CVD prevention in other populations if there is evidence that these proposed mechanisms are indeed protective.